Added day name to contributions calendar

## What does this MR do?

Adds the day name text into the contributions calendar tooltip.

## What are the relevant issue numbers?

Closes #19367 

## Screenshots (if relevant)

![Screen_Shot_2016-07-04_at_12.38.52](/uploads/edf6ac3454d479a345aee638875b7713/Screen_Shot_2016-07-04_at_12.38.52.png)

See merge request !5065